Conventional office chairs frequently have a tiltable seat assembly which tilts downwardly during rearward tilting of a back assembly. Such chairs include a tilt control mechanism which controls tilting of the seat and back assemblies and includes a tension arrangement which normally biases the chair to an upright position. Such tension mechanisms also include an adjustment mechanism for adjusting the return force generated thereby.
The invention relates to an improved tension control mechanism for adjusting the return force generated by a coil spring. The seat and back assemblies in this chair are functionally and structurally interconnected together in a four-bar linkage arrangement wherein the tension control mechanism includes an adjustment linkage connected between the coil spring and a front link of the four-bar linkage. An actuator adjusts a front end of the adjustment linkage vertically along the front link to vary the operating characteristics thereof and thereby adjusts the return force.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the system and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.